Water entry detection method and apparatus



May 6, 1958 G. P. MALY WATER ENTRY DETECTION METHOD AND APPARATUS FiledJani 14, 1957 Aarau/maj lua/afl WATER ENTRY DETECTIN METHOD ANDAPPARATUS Application January 14, 1957, Serial No. 634,018 14 Claims.(Cl. 324-4) This invention relates to a well logging method andparticularly to an instrument for determining the cornposition of fluidsentering a well bore at various places along the permeable interval.Specifically the instrument detects the locations of entry of emulsions,wet oil, and water or brine.

Crude petroleum and other valuable uids are frequently produced from theearths subsurface through well bores in a condition wherein they arecontaminated with other fluids which enter the bore simultaneously. Thisis especially true in the production of crude petroleum in which salinewater or brine is produced with the oil. Since these uids are ordinarilypumped from the subsurface through the bore, an extensive degree ofwater contamination inordinately increases the pumping costs. Sometimesthe quantity of water so produced runs as high as nine times the volumeof oil pumped from the ground. Occasionally the water cut is higher andsuch excessive quantities render oil production uneconomic.

It is important to determine this information accurately in order thatappropriate selective plugging or other water shutoff measures may betaken so as to minimize the quantity of brine produced with crudepetroleum.

The present invention therefore is directed to an improved method andapparatus for detecting accurately the points or depth incrementsthrough which water and other water-containing streams enter the borefrom the surrounding formation.

It is a primary object of this invention to provide a method fordetermining the location and approximate composition of fluids enteringa borehole as a function of depth.

lt is a further object to accomplish this determination without abnormalinterruption of normal production of fluids from the bore.

lt is a further object to provide a method for logging thick or deepproducing intervals to determine the points or strata of waterintroduction.

A particular object is to provide an improved method and apparatus fordetermining water entry locations without the interruption of normalproduction operations and which method and apparatus may be used to logwater entry from iluid producing strata having thicknesses of up to 200Gfeet or more.

It is also an object of this invention to provide a simple apparatus orinstrument to be used in accomplishing the foregoing objects.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art as the description and illustrationthereof proceed.

Briefly the present invention comprises a method in which the foregoingobjects are realized by disposing a fluid-permeable resilient materialas a matrix concentrically around a perforated section of productiontub` ing and which may be compressed slightly in order to Statesfatent() F 2,833,983 Patented May e, s

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force the matrix against a section of perforated casing or against thewalls of iluid producing strata. The interior of the matrix is providedwith a plurality of superimposed electrodes spaced apart from oneanother at a distance of between about 0.25 and about 6 inches andspaced apart from the production tubing and the outer surface of thematrix. One desirable form of electrode is that of a ring runningsubstantially completely around the production tubing through thematrix. Running longitudinally through the matrix more or less parallelwith the axis of the production tubing is provided an electrode cableconduit containing a plurality of electrical conductors, one each ofwhich is connected to each electrode. This cable is extended to thesurface through the annular space between the casing and the productionconduit and is connected to suitable instruments located at the surfacewhich are adapted to measure and record the resistivity or conductivityof the matrix with the uids passing through between each adjacent pairof electrodes as an indication of the brine ingress location.

The logging operation according to this invention involves thedisposition of the fluid-permeable matrix at a selected position withinthe well bore opposite the permeable interval to be logged. The pump maybe disposed either above or below the permeable matrix and in eithercase is operated so as to cause the flow of fluids upwardly through theproduction tubing thereby drawing or permitting the fluids to flow fromthe fluidproducing strata into the annular space between the tubing andthe casing from which they are picked up by the pump and carried to thesurface. In the case of that part of the annular space occupied by thematrix, the permeable fluids ow radially therethrough between theelectrodes and enter the production tubing through a. special perforatedsection of tubing within the matrix. By compressing the matrix slightly,as by supporting part of the weight of the production tubing stringthrough the matrix against the wall of the casing by means of a naturalor artificial bottom, the matrix may be pressed against the perforatedcasing requiring the fluid to flow through the perforations in this partof the casing, then through the permeable matrix radially between theadjacent pairs of electrodes, and then into the production tubing.

The nature of the tluids so flowing between the electrodes, andparticularly their water content, is readily detectable by measuring andrecording the resistivity of the matrix through which the fluids areflowing between adjacent electrode pairs. To obtain a proper record, itis preferable to operate in either of the manners described below.

In one method of operation, the matrix is first saturated by flowingWater through it, followed by a flow of dry oil which may be eitherkerosene or crude oil obtained from the well bore being logged. Thisbrings the entire matrix to an equilibrium or reference condition,generally referred to as the restored state and in this state it has areference resistivity.

The matrix thus treated is positioned opposite that permeable intervalto be investigated with respect to water ingress into the well bore.

The well is placed on production causing the formation fluids to passthrough the annular matrix into the production tubing and during thistime a periodic or a continuous log is maintained recording theresistivity of the matrix between adjacent electrode pairs over theinterval being investigated.

There is no substantial resistivity change when the iluid produced issubstantially dry oil, and the change in resistivity is relatively slowwhen the fluid is merely wet oil, soinewliat faster when the huid is anoil` and water emulsion, and'it-changes-quite rapidly when'wa-ter withsubstantially no oil passes between the electrodes. Continued 'flowcauses thei'resistivity ofl the matrix to approach an equilibrium valuewhich `i`s`^"eh'articte'ris'tite of the fluid `ioiiving between 'eachpair' of electrodesi Before proceeding to investigate the adjacentl orariother producing interval, the restored' state 'is again' obtained byinjecting crude oil in the reverse direction through the tubing and thematrix; baci: into the form'a' tion previously investigated until theinstruments indi-` cate restored state resistivity b'eween eachadjabeiit electrode pairs. l

The test section is then relocated in the wellE bbr'ef,t`hematrixcompressed so as to press'its outer surface against thehuid-producing surface, production is begun from this interval, and thenew resistivity changes areagain recorded.

These steps are repeatedv to log the desired interval;

The other method is identical to the one described immediately aboveexcept that the matrix may be presatur'ate'd with oill before entering'the hole and the matrix is not returned to the restored state in eachposition or station; Instead,the'changes in resistivity to or toward newequilibrium values are logged. This is the faster of the two'meth'odsand involves 'no interruption of fluid production from the borehole.Again the steps are repe'ated at each new position to log the entireinterval where these are deeper than the matrix length.

In order to eliminate interference with the production, especially inthick producing intervals, the apparatus-is preferably provided withmeans for flowing the 'uis produced front strata above the test sectionor matrix into the production tubing inlet at which lpoint it maybepicked up by the pump and conveyed to the surface.

rSuitable'huid-permeable resilientv matrix materials include spongerubber, sponge cellulose materials, other resilient sponge (plasticmaterials, andthe like. The material also shouldhave a reasonably gooddielectric strength. It isjpreie'rred that the permeability of thematrixmatcrial be relatively high, such as at least about tien timesthat of 'the strata, so as to minimize any decrease in production fromthe fluid-'producing zone duringthe test.

"lfhe 'structure of apparatus of this invention andthe method in whichitis sedwill be more clearly understood by reference to the accompanyingdrawing in which: i

Figure 1 is a vertical elevation view in partial ,cros s section of acasing rborehole extending through a lfluidp'roduciiig permeablestratumnand Nshowing the instrunient of this invention,

Figure 2 is a transvefse cross section of the instrument and the wellcasing taken in the direetin lindicated in Figure 1, A

Figure 3 isV a graphical representation ofv typical data obtainedthrough the use of the instrument shown in Figure l, and

Figure'4 is an elevation view in c'ross 's'ect`i`onV of a modified formofthe apparatus ofFige 1.

Referring now more paiticillarly'to'Fi'gure l' z iv l hole is shownextending from the' e'arths siirff e 2 downwardlythrongh permeablestratiii br" 'st`rata" 14 and terminating in an impei eablebase'nientfoifniiatioiil. The borehole Vis provided 'withfc'asing' i8, wel head20, and that portion of the casiiigwhicti `extends"throug permeableinterval is proyided'w'ith yopenings".22"through whichthe fluids flowreadily into the borehole.

Extending substansuy eternity tmougn-casiagisjis production tubing 24whiclrmaybe provided with'pitnp' 26. The instrument ofthe'pre'sentinvention 'is'dispos'ed below pump 26 or in any eventnear'the lower "nd of the production tubing 24.` Theiiistiumentfcompris'es" as its essential lelements a perforated cylindrical con'i't28 disposed substantially vatthe axi'sfiof themboehleupp' stationarystop 30, lower movable stop 32, the resilient of annular shapedelectrodes 36 superimposed one above the other and ordinarily insulatedfrom each other in matrix 34, and false bottom or production tubinganchor 38. The lowest extremity 40 of the production tubing is open sothat formation fluid'sowing into the borehole belowthe instrument ofthisinvention may flow upwardly into the pump inlet or into-theproduction tubing. Also provided through the wall of the productiontubing i'supp'er inlet conduit 42l which' in an analogous fashionprot'lidesl an entry into the production tubing for` fori'nation lluidsowing into the borehole from that 'portion of the' stratum aboveftheinstrument of'this'invention.

The false bottom or production tubing anchor.38 is provided with acentralinlet tubing" portion 44 which in turn is provided with a conicalsection 46. Surrounding this cylindrical portion is a cylindrical jacket48 provided with J slot 50 into which is received 'bo'ss or projection52 which extends from the outer surface of lower'cylindrical inletsectionV 44. `lso provided around the outer surface of jacket 4'8 is aplurality of spring steel friction bars 54. These press against theinner surface of casing 18 with sufficient' force' to support the weightof jacket 48 and its associated apparatus elements, including thetoothed anchor elements 576' which are hinged at the upper end of jacket48 b'y pivots S8.

As' thel instrument is lowered through the boreholein't'o the positionof irst use, the inlet conduit 'projection 52 is in the position at thetop and to the left of J slot 50; In thisposition cylindrical element W4is'r'ais'ed with respect to jacket 4S, conical element 46 isalsoz raisedvvso that its'up'per position is at a level corresponding-to the top ofanchor elements 56. This prevents the anchor Velements` from engagingwith the inner surface* ofy the casing andypermits the instrument to be'freelyfm'oved through the bore. This also increasesthe 4distance'betweenupper and lower stops 30 and 32, 'decompresse's the resilientfluid-permeable matrix 34, and permits this material to move freelythrough-the bore.

AThe instrument may be madesuiciently long between stops 30 and '32 s'othat the fluid-permeable matrix may extend entirely from the top to thebottom of a production interval. OrdinarilyV with thickA strata theinstrumentis moved from station to station through the' permea-bleinterval to obtain complete data regarding the composition of uidsentering the bore-atl all points along this interval. In Figure 1 thefluid-permeable' matrix isshown considerably shorter in length than thedepth of permeabile stratum 14.

In beginning the logging of such` a' thick stratum,the instrument ismoved to a position at the top or at the bottom of the interval. Theproduction tubing'is'th'en turnedV counter-clockwise causing projection52 to move to the right in J slot 50. While thefriction bars 54- supportthe weight of anchor elements 56' and jacket 48 the entire tubing stringis lowered moving projection S2 through the vertical portion of J slot50,. and this causes conical element 46 to engage anchor elements S6with the inner surface of the borehole casing. This downward movementsimultaneously compresses the resilient huid-permeable matrix andpresses its exterior surface uniformly against 4the casing wall, orformation wall'sif maybe used instead of the typical oneishow'n inFigure` l.

The normal fluid'ow from each'stratum in the interval encompassed by thevertical height of the `iiuid-permeable matrix continues withoutinterruption through the casing perforations, through the'huid-permeable matrix between the superimposed electrodes,an`d entersthe production tubing through perforations 60 provided therein. Fluidsproduced frori-ithe permeable formation above and below the intervalVencornpassedby Vthe matrix enter the production tubing through'npperinlet ctnltluit42` 'and lower opening 40 into lower inlet conduit44 in the mannerreferred to above.

Each of the individual electrodes is attached to a separate conductorcontained in conductor 4cable 62 and is thereby connected to resistivityrecorder 64 located at the surface.

With the duid-permeable matrix initially in what is known as therestored state as dened above, the iiow of uids through the permeablematrix causes a deviation in resistivity of the matrix from thatdetermined at the beginning of the run and corresponding to the restoredstate. Normal production is allowed to continue for a period suiiicientto obtain either a clear indication of the rate of change of resistivityof the matrix increments between each pair of electrodes, or a clearindication of a new equilibrium resistivity. This will be discussedfurther in connection with Figure 3. This provides data from which thecomposition of fluids entering the borehole between these electrodes maybe determined.

At the end of a given run with the instrument in a single position,crude petroleum may be returned to the foramtion in the reversedirection through the permeable matrix to return it to its restoredstate. This step may be omitted if desired as indicated previously. Theproduction tubing is then lifted and turned clockwise to release thetubing anchor, the instrument is moved to a new location and reset, andanother run is made during which additional resistivity changemeasurements are made. This procedure is continued until the entirepermeable interval has been logged.

Referring now more particularly to Figure 2, a transverse section of theinstrument shown in Figure 1 indicates perforated casing 18, theresilient duid-permeable matrix, one of the annular electrodes 36, theperforated production tubing section 60, and the upper inlet conduit 42.Shown more clearly in Figure 2 is conductor conduit 66 extendingvertically through matrix 34. At a point opposite the end of eachelectrode 36 an insulating means 63 is provided in the wall of the cableconduit. Conductor 7) extends from conduit 66 through the insulatingmeans 68 and provides an electrical connection at point 72 with each ofthe electrodes 36.

Referring now more particularly to Figure 3, a graphical representationof typical data taken with the instrument of this invention during theruns at the rst two stations is given. In this chart the measured matrixresistivity between individual electrodes is plotted against theduration of each run. Point 74 indicates the high resistivity of thematrix in the restored state after passage therethrough of dry oil. Asindicated by curve 76 this resistivity remains substantially constantwhen dry oil is produced through the electrodes from a given part of theformation at station one. Curve 77 indicates the resisitivity changewhen water is passed through the matrix in station two. Curve 78indicates the relatively gradual decrease of the measured resistivitytoward an equilibrium value when wet oil is produced from the formation.Such wet oil may contain up to about 20% by volume of water. The brokenlines on either side of curve 78, and of curve S subsequently described,indicate the approximate limits of the resistivity variation with watercontent for the particular material. Curve 79 indicates the subsequentchange at station two when emulsion is produced through the matrix.Curve 80 indicates the more rapid resistivity decrease when a water andoil emulsion is being produced from the formation at station one, andcurve 81 indicates the subsequent change when dry oil is produced atstation two. Curve 82 shows the extremely rapid resistivity decreasewhich occurs when water or brine is being produced at station one, andcurve 83 shows the subsequent change toward a new equilibrium value withow of dry oil at station two. The method used at station two is thesecond mentioned above. If the iirst method is used the data all followthe curves shown in Figure 3 for station one.

It is seen from Figure 3 that the detected change in resisitivity withtime indicates quite clearly the composition or nature of fluids beingproduced from a small increment of the formation'which is immediatelyopposite a given pairof electrodes. In this way a stratum producing dryoil is readily distinguishable from one producing wet oil, and from oneproducing an emulsion, and from one producing brine. Likewise, these maybe distinguished from one another and appropriate remedial measures maybe taken as are necessary in any given situation. The most commonsituation of course is the detection of brine entry and the shut-olf ofthese formations producing brine.

Referring iinally to Figure 4, a fragmentary view of a modiliedpermeable matrix 34 is shown including a plurality of superimposed,spaced-apart, impermeable annular ilow directors of resilient material.These positively prevent vertical ow through the permeable matrix. Anyresilient material which is stable in the environment may be used, suchas rubber, synthetic rubber like neoprene, and resilient resins.

Electrical properties of the matrix, other than the re-` sistivity, maybe measured in modifying the method of this invention. Such otherproperties include the magnetic permeability, the dielectric constant,the power factor, the capacitance, the impedance, and others. Of course,direct current or alternating current voltages are applied to theelectrodes as appropriate to measurement of the particular propertyselected. With crudevpetroleum and brine, probably the resistivity mostreadily distinguishes the various uids involved fromeach other.

A particular embodiment of the present invention has been hereinabovedescribed in considerable detail by way of illustration. It should beunderstood that various other modifications and adaptations thereof maybe made by those skilled in this particular art without departing fromthe spirit and scope of this invention as set forth in the appendedclaims.

I claim:

1. A method for logging a Huid-producing permeable interval penetratedby a borehole whichmcomprises disposing a fluid-permeable matrixenclosing a plurality of superimposed spaced-apart electrodes in saidborehole at a known depth opposite said interval and surrounding aperforated section of production tubing, said matrix being intiallysaturated with a known fluid giving said matrix between pairs ofelectrodes a known electrical property, removing iluid from saidborehole through the production tubing thereby permitting flow of fluidsthereinto from said permeable interval through said matrix, andmeasuring said electrical property of said matrix between said pairs ofelectrodes to determine the nature of iluid flowing therebetween intosaid borehole.

2. A method according to claim l wherein said electrical property is theresistivity of the Huid-containing matrix.

3. A method according topclaim l in combination with the steps of movingsaid matrix from station to station in said borehole throughout saidpermeable-interval at known depths and repeating the measurement of theelectrical property at each station.

4. A method according to claim 3 in combination with the step ofresaturating said matrix with said known iluid at each station aftermeasuring said electrical property at said station and before moving tothe next station.

5. A method according to claim l wherein said fluidproducing intervalproduces crude pretroleum, said known fluid comprises a substantiallydry hydrocarbon oil, said electrical property is the resistivity of saidmatrix, and wherein said resistivity remains substantially constantafter treatment with said dry hydrocarbon oil when dry petroleum owsthrough said matrix, said resistivity decreases to a lower value whenwet petroleum flows therethrough,-said kresistivity decreases toavstilllower value when emulsion flows therethrough,andsaidresistivityvdecreases to the lowest value When-Water owstherethrough.

6.- An apparatus for loggingauid-produeinig-permeable intervalpenetrated by a borehole which comprises an elongated production tubingextending from the earths sur-face' downwardly `through said borehole-to said permeable interval, aproduction tubing anchorydisposed-adjacent the lower end of said tubing and operable-from thesurface, said production tubing being provided*z with an elongated;perforated section adjacent said anchor, a fluid-permeable resilient4matrix of annular-shaped cross section surrounding said perforatedsection, a plurality of superimposed spaced-apartl electrodes disposedin the interior of said matrix, means above andbelow said matrix adaptedto compress itand thustpress the outer surface of said Vrn'atrilf`against Vthe surrounding surface ythrough wliieliuidsentei saidborel'ile` from saidintrval'wh'ereby' s'aiduids flowf'roh said surfacethrough said matrix between said 'electrodes' into said productiontubing, an electrical cable cont'aini'rigaplurality of conductors, oneconnected to each of said electrodes, extending through sai-d boreholeto the surface, an'dmeans locatedt at'the surface and connected to vsaidcable' adapted to measure an electrical property of said matrixbetween'ele'otrodes.

7l An apparatus according to claim 6 in combination with a reciprocatingpump' disposed above and in uidreceiving relation tov the perforatedsection of said production tubing.

8. An apparatus'according to cla'i'rn' 6 wherei'ne'acli of saidelectrodes comprises a ring embeddedwithin said matrix 'and extendssubstantially entirely around said perforatedsection of production"tubing;

9.- An-apparatusfaccording to'v claim 6 wherein the uid permeability ofsaid matrix is high relative tol that of the -permeable interval so as'to 'exert-substantially no flow restriction on thefluids*lloWingtherethrough.

110, Anlapparatus according to-clairn 9 wherein the permeability of saidmatrix is at least about tentimes greater than thatof Asaid interval;

4l1. l.lnap'paratusaecording to claim 6 wherein said electrodes arespaced vertically apart from each other by -a distance of between about0125 and about 6.0 inches.

l2. An-apparatus according to claim 6 wherein the lower end ofsaidproduction tubing is open to receive fluids producedfrom that part ofYthe permeable interval belowa said matrix, vandi said` pioduction tubingfis=fu1tl1er provided withV an upp'erinlet opening to receive iluidsproduced from tl'iatpart of thiefpermeablev interval above said' matrix.

v15. A'n apparatus" according to' claim 6 in combination withapliir'a'lityvf resilit nonpe'ie'able annular-shaped uid flowdireetorsdi's'posd between' `said electrodes to prevent ui'd flow"vertically' withinz said' matrix.

r4; Afl-apparatus awarding-t0 6 wherein said means* adapted to compress'said matrix comprises an upper' stationary stop" di' annular Shapedisposed around .an-d securedto"`saidf`produetion tubing and' a' lowermovable'` stopf'o'f annular' Shape disposedV around said productiontubing and "slidablyv supported on said tubing anchor.

References Cited in' the .le ofi thszpatent leunen" soirees' Parleurs21.539,35'5 lReiehertz Jan. 23, 1'95'1

